Don’t do that. Advertising any third party link can be seen as self promotion. Streamers in particular tend to get penalized for trying to list their stream in the group finder to promote it.
Once you form a group, if you need to give out a discord for coordination, that is fine to do in raid chat. Self promotion should be avoided at all times. If Blizz wants to promote someone’s social media they will do it through their launcher and media. Otherwise, they don’t want their platforms used for advertising.
Not even for girl scout cookies!